Cushion for backrest of chair



FIG. 1 is front view of the cushion for backrest of chair showing my new design;

FIG. 2 is a rear view thereof;

FIG. 3 is a right perspective view thereof;

FIG. 4 is a left perspective view thereof;

FIG. 5 is a right view thereof;

FIG. 6 is a left view thereof;

FIG. 7 is a top view thereof; and,

FIG. 8 is a bottom view thereof. 

CLAIM The ornamental design for a cushion for backrest of chair, as shown. 